combine breaks when passed two streams that share a parent

Here is a runnable reproducer:

import assert from 'assert';
import xs from 'xstream';

function Counter (click$) {
  const count$ = click$
    .fold((total) => total + 1, 0)
    .remember();

  return {
    count$,

    countString$: count$.map(count => count.toString())
  };
}

const click$ = xs.create();

const counter = Counter(click$);

const combinedStreams = xs.combine(
  (...vals) => vals,
  counter.count$,
  counter.countString$
);

const expectedValues = [
  [0, '0'],
  [1, '1']
];

combinedStreams.addListener({
  next(vals) {
    console.log('expected:', expectedValues[0], 'actual:', vals);
    assert.deepEqual(expectedValues.shift(), vals);
  },
  error(err) {
    throw err;
  },
  complete() {}
});

click$.shamefullySendNext();

 $ ./node_modules/.bin/babel-node test.js
expected: [ 0, '0' ] actual: [ 0, '0' ]
expected: [ 1, '1' ] actual: [ 1, '0' ]

AssertionError: [ 1, '1' ] deepEqual [ 1, '0' ]

We expect to see that the count$ and countString$ are equal, but only the count$ increments on click$.

If you pass countString$ as the first stream to combine, the opposite happens.

This use case is important for @cycle/collection, for combining multiple sinks on each item.

I’m unsure if this is a bug, or if I’m just misunderstanding something fundamental.

[Widdershin]

@ntilwalli I can no longer reproduce this issue in the latest version of xstream, so please consider this issue done and dusted. Thanks for your help 😄

[ntilwalli]

@Widdershin I’m not able to replicate the behavior you describe on webpackbin. If you look here (I posted your exact code but removed the assert) you’ll see the second stream does increment (http://www.webpackbin.com/Nk9ZrTGHb). Can you post a bin which demonstrates the odd behavior?